Is the word festas the same in Brazilian and European Portuguese?

Yes

The only difference between the use of "festas" in Brazilian Portuguese and Continental Portuguese is pronunciation.

In Brazilian Portuguese, the vowels are typically more open and clearly articulated; the "e" in festas is pronounced with an open sound. In Continental Portuguese, unstressed vowels are often "reduced" or "closed." This means the "e" in festas sounds much shorter, more muffled, or almost disappears, giving the word a more "clipped" or consonant-heavy sound. The meaning, spelling, and grammatical function remain identical in both dialects.

Brazilian Portuguese Examples

1. Eu amo ir a festas de aniversário. (I love going to birthday parties.)
2. As festas de Carnaval são as melhores! (Carnival parties are the best!)
3. A gente gosta de fazer festas em casa. (We like to have parties at home.)
4. Essas festas de rua são muito legais. (These street parties are very cool.)
5. Vamos organizar umas festas para as crianças. (Let's organize some parties for the children.)

Continental Portuguese Examples

1. As festas de Santo António são uma tradição. (The Saint Anthony festivals are a tradition.)
2. Costumamos ir a muitas festas no verão. (We usually go to many parties in the summer.)
3. As festas populares são muito divertidas cá. (Popular festivals are very fun here.)
4. Ele não gosta de festas demasiado barulhentas. (He doesn't like overly noisy parties.)
5. Organizámos umas festas para os miúdos. (We organized some parties for the kids.)